copying and saving stacks

I have a revolution stack and it works great.
In the Finder (Mac OS X) and made a copy of it and changed it's name.
When I opened it the stack property name also needed to be changed which I did.
Now I have two stacks that are essentially exactly the same except
they are named differently in the file system and they have different
stack name properties.
So why is Revolution balking at me when I try to open both at the same time?
Asks me if I want to purge the other one when I open the second stack.
What is up?
Kee Nethery